Apparatus for detecting flame



July 26, 1960 c. J.K| E|N APPARATUS FOR DETECTING FLAME Filed Sept. 14, 1954 NWN mn@ MNNLTKNRLANRH se n @SFN www INVENToR. (jjbfa Ja/fz e/Zz i ATTORNEY 2,'946g99'o Y .APPARATUS roRnErfEcTnsIGfFLAr/IE -vclifror'd fig-1m "Klein, Rverile NlI., Aassigner to ispe- =clties Development tCorporation, tBelleville, iNJ., a

corporati'onofNewFJe'rs'ey Y Y .Filed'sept.;12t,.19s4,ser.No..455,921-, 6 claims. (cream-izan i 'The Ipresent;invention V.rela-tes to Ydetecting 1iame,-and, .more ,.particularly, to v4an improved radiant fenergy isensitive` apparatus .for Idetecting flame .-in response tor-llame frequencies.

It is well lknown `that Ythe A.flame -of=combustiblema terialsilickers at lfrequencies lbetween about -'4 ancha'bout 20,000 cycles l persecond due 'tofan vuneven burning ,proc- .ess which results inthe emission of radiant'energyfincluding visible-and invisible light; and.tlratsuiicient.radi .antenergy in YtherangeofV .5 to 30--cycles per second is emitted to i. assure -its detection. Radiant-energy atlsuch .flicker frequencies can bedetecte'dbyradiant energytsen- Ys itive ydevices such Lplrotoelet-:tricxcells or tubes Tand :the like, coupled `withapparatus Fhaving -an output, :respon- ..sive only yto `these flicker "frequencies, l which output can .:be utilized to @control means .for .'ind-icating'lthat @such Y ffl-iig. 2 .is a block `flicker.frequencies are "-being detected i-,Gonsequentlyi l dire detecting -apparatusthas beendevised which utilizes i v z. .thisiphenomenon topper-ate an'-aljarm forfindicatinggthe presence of ame and/or for initiatingfoperatiomofa.fire `extinguishing system. Y

q V:agregar Y .Patented :.lulyZS, ,i960

`tobviousfuponlanunderstanding offthe illustrative-embodi- `:ment about to .be described,or willibefindieatedxinithe V appended claims, and various .advantages notv referredito v off the specification, wherein:

Fig. .1 .is a :graphic illustration lof radiant `energy `waves.

1- `detected .in`- a llame which waves have' Iickerwfrequency modulation. Y v Y diagram illustrating v 'one .form .of -iiame `detecting- 'apparatus in 'accordance with the `invenrtion. l Y y Referring to Fig. 1 orl the drawing-the.radiationwaves detected ailame arepg-raphically. illustrated-as recorded Aby van oscillograph. While `such waves actually -vary .1 greatly in amplitude and iin fundamental frequency, v.they

.ly as shown to 'more clearly illustrate Athe same, and :occur-at aifrequency .'offbctween fabout -1 :and about :Y10 n-cycles per fsecond, iforfexample, at 3 .cycles per `-second v .as shown herein. 'Ihisphenomenon may becharacterized as dame .iiickerfrequency modulation F -Mf, and .can be ,-fdetect'ed andythen transl-ated into-'electrical fenergy ffor -jcontrolling-l indicating -mea'ns in fresponse terist-ics of the flame observed. 35 yIt has l.been found-fthat such systems chave".nnmerousV disadvantages when installed in locations where radiant energy from a source other' than fcielt-air1l conditions; `can` affect' the` fd ice. -For example,"on-board tof a flame,"` under t energyjsensitive aft or otlrercraft Jected'ito mechanical "vibrations" the radianr'energv `to l -the i charac- I "InfFig' 2,.fthe r'e isrshown a block-diagrammi .apparatus :for detecltiug flicker frequency modulation :in aiilame @converting A[the ,radiant energy *toaeleetrical rencrgys rand which is periodically interrupted due to vibrations. In the event the frequencies of such light or radiant energy interruptions are within the band of flicker frequencies sought to be detected, the system may be subjecte'drto false operation which is highly undesirable.

In accordance with the present inventiomit has been discovered that the frequency at which a dame iiickers variesconstantly, and that such ilicker frequency van'ations, Within a given period of time, follow a recognizable pattern havingv a frequency or band of frequencies of its ownfwhich' in a sense is comparable to frequency modulation as used in FM radio transmission. Consequently, it'is now proposed to utilize this frequency modulation phenomenon to discriminate between flame iiicker and light or radiant energy chopping or the like and thereby eliminate false operation.

Accordingly, an object of the present invention is tov `the iiicker'ing of a lamp connected in a faulty circuiti#5 :literature -detailed illustration -and description @thereof :fare lbelieved ,toV be unnecessary.

`apparatus*illustrated herein essentially-comprises afilamedetecton a band pass amplifier, ya limiter, a'rfreand an indicator.

The iiame detector is a device capable of detecting the quency rmodulatio'n k"detectorand discriminator, a relay,

radiant energy o-f `an open ame and responding the-reto Y to produce an electrical signal corresponding substantially to the radiant energy being emitted. Preferably, this delvice is any one of the many types adapted to detect radiations in the infra-red region of the dame spectrum, Whereby to render the apparatus insensitive tol radiations in other regions of the spectrum- For example, `such a dev-ice may be abolometric tube, a lead sulphide cell or their equivalents. i

The `function of the band pass amplifier is to amplify the flame detector' output Within a certain band of frequencies so that the radiant energy of even the smallest detectable ilame at the commencement of a fire causes the apparatus to give an indication thereof. However, since the amplitude of the radiant energy of a minimum flame and that of a ame of a raging fire varies so greatly, a limiter is used which functions to conne its output Y to a predetermined maximum amplitude including the peaks of all the ampliiied Waves detected in a minimum prising conventional electrical components arranged in.

Well known circuits'which are combined inA a novel manner.

@ther and further objects of the invention ywill be flame but excluding the peaks of the waves of higher amplitudes. The limiter thereby removes any amplitude modulation, whereby the output signal of the limiter has a wave` pattern similar to the portions of the waves within the zone L defined by the parallel broken lines in Fig. l.

duce a signal in response to a given frequency of such fluctuations or Within a given band of such fluctuations, for example, 1 to 8 cycles per second. Since the wave shown in Fig. 1 has a modulated frequency of 3 cycles per second which falls within the band to which the discriminator may be tuned, the discriminator produces an output signal in response to such modulated frequency.

- From the foregoing description, it will be seen that the present invention provides `a simple, practical and reliable apparatus for detecting a flame which eliminates The function of the relay is to enablethe signal or output of the discriminator to cause an indicator to be operated. Since the discriminator output is notof a Y value sufficient to operate a lamp, bell, buzzer or other indicator, the output is utilized to trigger a thyratron which controls an electro-magnetic relay adapted to closel a switch in the indicator circuit. v

all possibilities of false operation due to radiant energy varying at a constant frequency, it being inconceivable that signals produced by such `a source would have a modulated frequency corresponding to a value within the band to which the discriminator is tuned.

2. In a flame detecting apparatus, the combination of -an infra-red energy detector, means controlled by said detector having an output responsive to flame icker frequencies, ya frequency 'modulation discriminator for producing a signal in response to variations in the flicker frequency of the output, and means controlled by the signal of said discriminator for giving an indication that frequency variations are being detected. l

3. In a ame detecting apparatus, the combination of means having an output responsive to flame flicker frequencies, means for controlling the amplitude of the output, means for detecting variations in the frequency of the output, and means controlled by said `last mentioned means for giving an 'indication that a variation in frequency is being detected. y

4. In a flame detecting apparatus, the combination of means having yan output responsive to arne flicker frequencies, means for limiting the amplitude of theoutput,

means for detectingvariations in the frequency of the limited output, and means controlled by said last mentioned means for giving an indication that a variation in frequency is being detected.

5. In a flame detecting apparatus, the combination of means having an output responsive to ame icker frequencies, means f or'amplifying the output and Hunting the amplitude of the output, means for detecting variations in 'the frequency of the output, and means controlled It will be understood that the frequency values to which the apparatus is tuuedare illustrative only, and that the apparatus is adapted to be utilized in connection with the detection of radiant energy within any desired band of frequencies of the tiame icker spectrum. A-lso, the present invention contemplates that frequency modulaf tion within-the output signal of the FM discriminator can be detected and discriminated stage-wise, ad infinitum,

whereby toV `operate the indicator in response to very specific flame flicker frequency patterns.

struction and arrangement ofthe partseherein, without departing'from the spirit and scope of the invention and without sacrificing any of its advantages,- it is to be understood that all' matter herein is to be interpreted as illustrative and-not'in any limiting sense. A

I claim; Y Y 1. 'In a ame detecting apparatus, the combination of means having an output responsive to flame flicker by said last mentioned means for giving an indication that a variation in frequency is being detected.

6. In a llame detecting apparatus, the combination of an infra-red energy detector having an output responsive to ame flicker frequencies, a band pass amplier and are'be'ing detected.

As=v`arious changes may be made in the form, con-"M40 limiter network for controlling the output, a frequency 35' modulation discriminator for producing a signal in reput, and means controlled by the signal of said discrimisponse to variations in the frequency of the network outnator for giving an indication that frequencyV variations References Cited in the tile of this patent .I UNITED STATES PATENTS 21,349,715 Francis May 23,1944 2,607,899 Cary et al. Aug. 19,'1952 2,655,645 Bango Oct. 13, 1953 12,722,677 v Krueger Nov. 1, 1955 2,749,447. Smith June 5, 1956 2,811,711 Cade et a1. Oct. 29, 1957 1958 2,834,008 Carbauh May 6, 

